Recording materials, to which the principle of color development resulting from the reaction between a color developing dye and a developer is applied, have been widely used for thermal papers for output recordings by facsimile machines, printers or the like or pressure sensitive copy papers for slip pads simultaneously transcribing multiple sheets, because these recording materials are capable of recording by using a comparatively simple recording apparatus in a short time without undergoing any troublesome procedures such as development and fixing. It is required to develop, as the recording materials described above, those which can develop color faster, retain clear whiteness of the uncolored area (hereinafter referred to as “background”), and also provide high toughness in images, especially excellent light resistance in the images in view of long-term storage stability.
2,4′-dihydroxydiphenylsulfone has conventionally been known as a developer having excellent light resistance, but was still unsatisfactory. As a method for solving these problems, Japanese Patent Application, First Publication No. Hei 8-290661 and Japanese Patent Application, First Publication No. Hei 10-264531 describe that excellent light resistance of the images is achieved by using 2,4′-dihydroxydiphenylsulfone in combination with specific dyes and coreactants. Also, Japanese Patent Application, First Publication No. Hei 7-25141, Japanese Patent Application, First Publication No. Hei 7-149046 and Japanese Patent Application, First Publication No. Hei 7-314894 describe that light resistance is improved by adding antioxidants and ultraviolet absorbers. However, these methods caused problems such as increase in manufacturing cost, various manufacturing processes, and complicated operations.
As compounds relating to the present invention, Japanese Patent Application, First Publication No. Hei 2-204091, Japanese Patent Application, First Publication No. Hei 1-72891, Japanese Patent Application, First Publication No. Hei 4-217657 and WO01/25193 disclose phenolic compounds as a developer. It is desired to develop a technique of providing an excellent recording material which exerts excellent effect on storage stability of the background and images.